Hexamita Infections in Freshwater Fish

Caring a fish is not just about feeding it, it’s also about watching for potentially serious health conditions. Sometimes we failed to see existing problems that somehow cause of various infection and disease. One of the major illness that is still unclearly understood is Hexamita disease, also known as "hole in the head" or "White Poop".

Hexamita is caused by various species of the protozoan parasite genus Hexamatiasis. It is very common on wild caught species and even in tank-bred specimens. This type of protozoan parasite usually affects on the family of Cichlidae such as discus, angelfish, oscars and gouramis. Once the parasites become established, it can multiply rapidly and spread into the other internal organs. The parasites infection may over-whelm the immune system resulting in serious disease and even led to death.

A infected fish commonly produce white stringy feces. The fish eventually lose their appetite and slowly become emaciated, which causes the color of the fish changed turn to be sallow. In certain conditions there is a wound that appears on the head of the fish, sometimes these wounds also apparent on the fish’s flanks.


The most effective approach to treat Hexamitiasis is using medicated food, especially for early infection treatment. For seriously affected fish it is strongly recommended to carry out the treatment by adding a medication to water. The prime medication used to treat Hexamitiasis is Metronidazole. Typically use one capusule of 250 mg Metronidazole per 10 gallon, once per day for at least three days.


The reason Hexamitiasis has been much studied by fish biologists because its prevalence on fish farms, where growing fish are often maintained at very high stocking densities. Overstocking, inadequate filtration, lack of water changes and insufficient oxygen are all critical factors that need consideration when diagnosing or treating Hexamita infections in fish.

The keys to maintain low levels of nitrate are to minimize the amount of food going into the water by not overfeeding, and to maximize the amount of water that has a high nitrate content well removed at each water change.


Not all fish that shed out white string-like poop has Hexamita. A fish that are exposed to new tank water or new diet usually shed out intestinal lining but this is only limited to a few days.

The relationship between Hexamita and hole in the head disease is reasonably well-established. But it is not certain that all cases of head and lateral line erosion disease in fish are caused by Hexamita parasites.

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